Unprecedented. That’s the way earthquake engineers are describing today’s seismic test at the University at Buffalo.
Most simulated earthquake tests feature neither full-scale structures nor ground motions in three directions, but the seismic test being conducted today in UB’s Structural Engineering and Earthquake Simulation Laboratory features both.
Constructed on the laboratory’s twin shake tables, the three-bedroom, two-bath, 1,800-square foot, wood-frame townhouse building being tested today is completely furnished, down to the car in the garage, two water heaters (one anchored, according to earthquake protection measures and one not anchored), and dishes on the dining room table.
It is the largest wood structure to undergo seismic testing in the world.
An upstairs bedroom has been decorated as a UB dorm room, by the university’s student chapter of the American Society for Civil Engineers. On the wall hang T-shirts from the project’s participating universities: UB, Colorado State, Cornell, Rensselaer Polytechnic Institute and Texas A & M.
Even a family of automotive crash dummies, including a father, a mother and a three-year-old child will temporarily "reside" in the home during the test.
"The goal of furnishing the house is to make the test as realistic as possible," said Filiatrault, UB professor of civil, structural and environmental engineering and lead investigator on the UB tests. "The test will demonstrate in a dramatic way how much damage can occur during an earthquake if homeowners don’t take the proper precautions."
Today’s test ends the first year of a four-year, $1.24 million National Science Foundation-funded project called NEESWood, designed to provide engineers with data on how to improve performance of wood-frame structures during earthquakes.
Led by Colorado State University, the NEESWood research is based on the premise that if more were known about how wood structures react to earthquakes, then larger and taller wood structures could be built in seismic regions worldwide, providing economic, engineering and societal benefits.
The NEESWood project will culminate with the validation of the new seismic design processes early in 2009, when a six-story wood-frame structure, pre-fabricated in the U.S. will be shipped will be flown to Miki City, Japan and tested on the world’s largest shake table.
Today’s simulation recreates the magnitude 6.7 Northridge earthquake that struck the Los Angeles area in 1994, and will generate ground motions in three directions, called "triaxial" motions.
"This test will create four times the shaking of the strongest of our previous tests, it’s what engineers call the ‘maximum design event," said Filiatrault. "It’s a very realistic test. This is a full-scale earthquake."
Constructed on twin shake tables last spring, the townhouse was subjected to five increasing levels of shaking in three dimensions, the most authentic ground motions that can be produced in a U.S. laboratory. The ground motions simulate increasing intensities that were recorded during the 1994 Northridge earthquake in the Los Angeles region.
During the test, 250 sensors installed inside the house will gather detailed information about how each component of the building behaves during the simulated earthquake. A dozen videocameras — eight indoors and four outdoors — will record the shaking as it happens.
According to John van de Lindt, Ph.D., associate professor of civil engineering at Colorado State University and the lead investigator for NEESWood, the UB benchmark testing already has begun to generate useful data on how to make wood-frame homes and buildings safer for occupants during earthquakes.
"The results from this benchmark test at UB will probably change the way we model wood frame structures," said van de Lindt. "That’s a huge advance because without those modeling tools, we would not be able to achieve our greater objective, which is constructing six-story wood-frame structures that perform better during earthquakes and provide an economical and sustainable construction solution."
The UB and Colorado State researchers say just minutes after the test, when they enter the house to conduct their inspection, they will have preliminary data about how much the structure moved and a general idea of the extent of damage.
Detailed evaluation of the data gathered by sensors and camera will take approximately six months to analyze, they said.
Earthquake engineers say such testing is long overdue.
While wood frame construction accounts for an estimated 80-90 percent of all structures in the United States and 99 percent of all residences in California, fewer than 10 percent of civil engineering students are required to study wood design.
In addition to Filiatrault and van de Lindt, co-principal investigators on NEESWood are Rachel Davidson, Ph.D., assistant professor of civil and environmental engineering at Cornell University; David V. Rosowsky, Ph.D., professor and head of the department of civil engineering at Texas A&M University, and Michael Symans, associate professor of civil and environmental engineering at Rensselaer Polytechnic Institute.